The basis for this K01 application is to study how the hormone leptin acts in both the brain and liver to positively regulate hepatic glucose and lipid flux and thus mitigate hyperglycemia and insulin resistance. To do so, I will develop expertise during the award period using stable isotope tracer techniques combined with mass spectrometry and nuclear magnetic resonance analyses of hepatic glucose and lipid fluxes. These are powerful methods that allow study of animals in vivo and measurements of functional effects on metabolic pathways. This will be done under the co-mentorship of Drs. Joel Elmquist and Shawn Burgess laboratory. Current targets of leptin action under study are POMC neurons in the ARH and direct leptin action on hepatocytes to regulate hepatic glucose and lipid metabolism. More traditional analyses of protein expression and gene expression will also be performed to complement in vivo findings related to function and identify specific molecular pathways that may be more directly targeted by pharmacotherapy. Future work could use metabolomic and microarray (or more advanced) approaches to identify unknown or under-appreciated metabolites and genes that vary between various genotypes. The current focus is to understand functional implications of physiological perturbations on flux. This focus does not undervalue or diminish the importance of findings related to molecular signaling or identification of novel regulatory components or targets. Instead, this emphasis recognizes the priority to develop expertise performing these experiments, analyzing/interpreting the data, and the ability to transfer these skills to other questions and/or other environments. Moreover, findings related to differences in molecular signaling and/or novel signaling may be the foundation for my goal to become an independent academic scientist. A final note related to this application is that ALL proposed genetically modified mice, reagents, and necessary equipment are in-hand and available to me for continued use. We are NOT proposing to develop novel research tools during this award period and can thus focus on training and completing the proposed aims.